1. Field of the Invention
The present invention relates generally to a feed-forward ring oscillator, and, more particularly, to a feed-forward ring oscillator using multiple independent gate field-effect transistors.
2. Description of the Related Art
Ring-type oscillators have been generally used as clock generation circuits because of their advantages in terms of good efficiency, a wide frequency range, and a small area. The frequency of oscillation of such a ring-type oscillator may be generally calculated using the following equation:fosc=1/(2Ntd)  (1)where N is the number of delay cells, and td indicates a delay time of a single delay cell. Since the frequency of oscillation of a ring oscillator is inversely proportional to N, there are limitations in operational reliability and the area of the oscillator when a large number of delay stages are used.
Feed-forward ring oscillators are ring oscillators that have been developed in order to overcome such limitations. The structure of such a feed-forward ring oscillator is such that a feed-forward loop is added to a ring oscillator in the existing type of manner. The delay cells of the existing feed-forward ring oscillator additionally require field-effect transistors in order to form input pairs used for the feed-forward loop.
The feed-forward ring oscillator having such a delay cell has the disadvantage of occupying a large area because of the additional field-effect transistors.